Instructions
Open your in-game map using the V.A.T.S. interface. Select the "Map" option. Select a point on either the top side or the bottom side of the in-game map. It doesn't matter whether the point is north or south on the map, just that it is as far north or south as you can go. Select the "Fast Travel" option to travel to that point on the map from your current location.
Begin to walk north (if you fast-traveled south on the map). Begin to walk south (if you fast traveled north on the map). As you travel, you will be periodically attacked by monsters and other giant creatures. Kill everything you see. Every creature you kill earns you experience points that are used to increase your level.
Heal yourself (after a battle). Depending on your current level, equipment and weapon selections, you may be seriously damaged during a battle. After you kill a monster, heal yourself and keep walking.
Repeat Step 2 and Step 3 until you are at Level 30. Leveling up in "Fallout 3" involves earning experience points. You earn these experience points during battle. The more battles you participate in, the faster you will level up.